Method of applying coatings to edible tablets or the like



Aug. 11, 1953 D. E. WURSTER METHOD OF APPLYING COATINGS TO EDIBLETABLETS OR THE LIKE Filed Jan. 21, 1949 RECOVER Y Alva Ex HA us 1- AIRDuscmme: ALONG WALL OF COMPRESSED OUTLET To Pou SHING PAN IN V EN TOR.

Patented Aug. 11, 1953 METHOD OF APPLYING COATINGS TO EDIBLE TABLETS ORTHE LIKE Dale E. Wurster, Madison, Wis., assignor to Wisconsin AlumniResearch Foundation, Madison, W1s., a corporation of WisconsinApplication January 21, 1949, Serial No. 71,997

6 Claims. 1

My invention relates, generally, to methods of and means for applyingcoatings, and it has particular relation to the coating of medicinaltablets, chewing gum, candy, nuts, etc.

Among the objects of my invention are: T support the tablets in air in acoating chamber and to coat the same While they are so positioned; tosupport the tablets in an upwardly flowing air stream; to heat the airprior to its contact with the tablets to dr the coating thereon; tocause the air to flow in a turbulent fashion and tumble the tablets sothat they may be coated uniformly; to move the tablets downwardly on abias transversely of the air stream while they are being coated; tointroduce the coating material into the air stream under neath itsinitial contact point with the tablets; to introduce individually intothe air stream different coating materials; and to direct a current ofair upwardly in the coating chamber along its inner surface to preventthe coating material from impinging thereon.

Other objects of my invention will, in part, be obvious and in partappear hereinafter.

This invention is disclosed in the embodiment thereof shown in theaccompanying drawing and it comprises the features of construction,combination of elements, arrangement of parts and method steps whichwill be set forth in detail hereinafter and the scope of the applicationof which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of myinvention, reference can be had to the following detailed description,taken together with the accompanying drawing, in which:

Figure l is a longitudinal sectional view of a coating mechanismconstructed in accordance with my invention;

Figure 2 is a View partly in section and partly in elevation at anenlarged scale showing in more detail the construction of the manifoldwhich directs air upwardly along the inner surface of the coatingchamber; and

Figure 3 is a top plan View of the rotating disc which causes the air toflow in a turbulent fashion. 7

Referring now particularly to the drawing, it will be observed that thereference character I'll designates a vertically positioned coatinchamber which may be formed of metal or glass. The coating chamber Illpreferably has a circular cross section, and it may be of conical,modified conical, or cylindrical shape as may be desired. Near its lowerend there is provided an entrance I I for the tablets to be coated. Aninlet tube [2 communicates with the entrance and slides l3 and 14 arepositioned therein to permit the introduction of the tablets to becoated into the chamber Ill in batches.

Within the chamber In there is a screen I which extends transverselythereacross and on a bias so that the tablets to be coated and whilethey are being coated move across the chamber Ill and downwardly to anexit ['6 with which an outlet tube ll communicates. The tube Il maydischarge into a polishing pan or similar receptacle. Slides l8 and Itmay be provided in the outlet tube I! for. controlling the flow of thecoated tablets theretln'ough in batches similar to the manner in whichthey are permitted to flow onto the screen l5 by the slides l3 and M.

It is desirable that the uncoated and partially coated tablets above thescreen l5 be supported in air so that they can be evenly coated. Forthis purpose air jets 20 and 2| are positioned in the lower end of thechamber Ill below the screen l5 and are directed upwardly to suppl anair stream flowing upwardly in the chamber H) of sufiicient velocity tomaintain the uncoated and partially coated tablets slightly out ofcontact with the screen l5. The air jets 20 and 2| may be connected byconduits 2B and 2| to a suitable. source of compressed air, the pressureof which is adjusted so as to maintain the uncoated and partially coatedtablets slightly above the screen l5 to be coated in a manner to bedescribed presently.

Not only is it desirable that the tablets be supported in the air streamwhich flows uD- wardly through the coating chamber I0 but also it isdesirable that they be tumbled so as to coat the same more uniformly.For this purpose the flow of air through the coating chamber II] isarranged so that, in place of it being a streamlined flow, it is aturbulent flow. For this purpose a disc 22 is provided which may berotated at a constant speed by a motor 23. As shown more clearly inFigure 3 the disc 22 has circular rows 24, 25, 26, and 21 ofperforations through which the air from the jets 20 and 2| flows. Asshown in Figure l the air jets 20 and 2| register with the circular rows24, 25, 26, and 21 of perforations so that the air from the former is drected byv the row of perforations individual thereto. Also as shown inFigure 1 the rows 24 and 21 of the perforations are inclined inwardlywhile the row 25 ofperforations is inclined outwardly. The remaining row26 extends Vertically through the disc 22. The several air streams thusdirected by the perforations 24, 25, 26, and 2'! impinge on the uncoatedand partially coated tablets above the screen IS in a turbulent fashionand cause them to be tumbled so that they can be evenly and completelycoated with the coating material.

With a view to drying quickly the coating material on the tablets,provision is made for heating the air as it passes upwardly through thechamber ll) underneath the screen [5. For this purpose an electricheater element 28, in the form of a grid, may be positioned immediatelyabove the rotating disc 22. It will be understood that the heaterelement 28 maybe connected for energization to a suitable Current sourceand that the degree of heat can be varied by varying the amount ofcurrent fl g.

therethrough.

The material for coating the tablets may be supplied through conduits30, 3| and 32, the number being determined by the number of differentcoating materials to be employed. Each of the conduits 30, 3| and 32terminates in a nozzle 33 which, as shown in Figure 1, is directedagainst the tablets near the upper edge of the screen l5 so that thecoating material is supplied to the tablets as soon as they pass throughthe entrance II. It will be understood that various coating materialscan be supplied. As illustrated in Figure 1, the conduit is arranged tohave powdered lactose blown therethrough. The conduit 3| carries anacacia solution, while the conduit 32 may carry a sugar solution. Itwill be understood that these particular materials are mentioned forillustrative purposes only and that other coating materials can be usedas may be desired.

Certain of the coating materials may tend to adhere to the inner surfaceof the coating chamber Ill particularly in the immediate vicinity of thescreen l5. In order to prevent this a ringlike manifold 34 may bepositioned just above the screen I5. As shown in Figure 2 the manifold34 has outwardly and upwardly directed openings or apertures 35 whichcause air supplied to the manifold 34 from a suitable source ofcompressed air to flow in the directions indicated by the arrows 36 overthe inner surface of the chamber In for preventing the coating materialfrom engaging the same.

At the upper end of the coating chamber II] a screen 31 may be providedto prevent the escape of tablets in the event that the pressure suppliedthrough the jets 20 and 2| should be sufficiently great as to cause themto rise to this position. An exhaust tube 38 connects the coatingchamber II) to a suitable recovery and exhaust chamber as will beunderstood readily.

In operation, the motor 23 is energized to drive the disc 22 at thedesired speed. Air under pressure is supplied through the conduits 20'and 2| to the jets 20 and 2| respectively so that the uncoated andpartially coated tablets on the screen I5 will be tumbled thereabove.This air pressure also is adjusted so that when the tablets are fullycoated it will be insufficient to maintain them above the screen l5 atthe lower end thereof adjacent the exit [6. The current flowing throughthe heating element 28 is adjusted so that the coating applied to thetablets above the screen I5 is dried satisfactorily. The coatingmaterials supplied to the conduits 30, 3| and 32 are arranged andadjusted so that the desired proportions will be applied to the tabletsat rates which will provide the desired thickness of coating. Air issupplied to the manifold 34, it being understood that the pressure atthe apertures 35 therein is slightly greater than the air pressure atthe air jets 20 and 2| so that the desired air flow takes place alongthe inner surface of the chamber [0 to prevent the coating material fromimpinging thereon.

Now, the slide I3 is raised to permit a charge of uncoated tablets toflow downwardly through the inlet tube I2 against the slide Id. Theslide I3 is closed and then the slide I4 is opened. The uncoated tabletsflow through the entrance II onto the upper end of the screen I5 and areimmediately lifted thereabove and tumbled. At

4 the same time they are subjected to the atomized flow of coatingmaterials from the nozzles 33 which are supplied individually by theconduits 30, 3| and 32 in the manner described. The partially coatedtablets move transversely of the chamber .IO and downwardly on a biasbut are still being tumbled above the screen l5 until the coatingthereon is sufficiently heavy so that the upwardly flowing air stream isinsufficient to maintain them out of contact with the screen '|5. Whenall of the tablets have been completely coated, the slide I8 is openedand they are allowed to dischargethrough the exit l6 into the outlettube II. Thereafter the slide 18 is closed and the slide I9 is opened topermit the coated tablets to be discharged into the polishing pan orother receptacle as may be desired.

It will be obvious that certain changes can be made in the foregoingconstruction and method without departing from the spirit and scope ofthis invention. Accordingly, it is intended that all matter shown in theaccompanying drawing and described hereinbefore shall be interpreted asillustrative and not in a limiting sense.

I claim as my invention:

1. The process of covering eatable tablets of the type of medicinaltablets, chewing gum, candy and nuts with a sugary coating whichcomprises: moving an air stream in a confined space upwardly past theeatable tablets with a force sufiicient to suspend them continuouslytherein, and introducing the sugary coating material into said airstream prior to its contact with the eatable tablets.

2. The invention, as set forth in claim 1, wherein the coating is wet onapplication and the air stream is heated to dry quickly the coatingapplied to the tablets.

3. The invention, as set forth in claim 2, wherein the air stream isturbulent to tumble the tablets whereby they receive a coating ofuniform thickness.

4. The invention, as set forth in claim 1, wherein the tablets movedownwardly on a bias transversely of the air stream while being coated.

5. The invention, as set forth in claim 4, wherein the coating materialis introduced into the air stream at a position close to the initialcontact point thereof with the tablets.

6. The invention, as set forth in claim 1, wherein the coating materialcomprises a plurality of different materials and they are introducedseparately into the air stream.

DALE- E. WURSTE'R.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,473,165 Steigmeyer Nov. 6, 1923 1,546,922 Faber July 21,1925 1,725,608 Zebulski Aug. 20, 1929 2,059,983 Dent et al. Nov. 3, 19362,259,879 Denning -1 Oct. 21, 1941 2,339,932 Kuhl Jan. 25, 19442,349,230 Thomas May 16, 1944 2,399,717 Arveson May 7, 1946 2,447,006Gamson Aug. 17, 1948 2,459,836 Murphee Jan. 25, 1949 2,491,632 WiederDec. 20, 1949 2,493,198 Kelley, Jr. Jan. 3, 1950 2,498,405 Fader Feb.21, .1950 2,536,168 Goggin Jan. 2, 1951 2,561,392

Marshall July 24, 1951

1. THE PROCESS OF COVERING EATABLE TABLETS OF THE TYPE OF MEDICINALTABLETS, CHEWING GUM, CANDY AND NUTS WITH A SUGARY COATING WHICHCOMPRISES: MOVING AN AIR STREAM IN A CONFINED SPACE UPWARDLY PAST THEEATABLE TABLETS WITH A FORCE SUFFICIENT TO SUSPEND THEM CONTINUOUSLYTHEREIN, AND INTRODUCING THE SUGARY COATING MATERIAL INTO SAID AIRSTREAM PRIOR TO ITS CONTACT WITH THE EATABLE TABLETS.